In my earlier U.S. Pat. No. 4,021,343, issued May 3, 1977, there is shown and described an automatic water purifier system requiring no electricity. The water is always fully enclosed, so that it is not exposed to insects or air-borne bacteria. There is no back pressure on the membrane, nor is there wastage of water after the pure water tank is full.
However, the above and other advantages set forth in U.S. Pat. No. 4,021,343 were achieved at the expense and inconvenience of having: (a) at least three tubes to the spigot (faucet) assembly, and (b) two manually-operated valves in such assembly. When three tubes are thus used, it becomes difficult or impossible to locate the spigot at a substantial distance from the remainder of the system. Thus, for example, piping of the pure water to the automatic icemaker in a household refrigerator is usually not feasible. The use of pure water in icemakers not only prevents the ice from being bad-tasting but also causes it to be clear and unclouded.
A single-tube system having the advantages stated in U.S. Pat. No. 4,021,343 has now been achieved. Furthermore, the present purifier system is much more simple, economical, rugged, reliable and maintenance-free than is that described in the patent.
A very great problem present in my earlier system, and in all other earlier systems having any degree of practicality, is that of fouling of the waste outflow constrictor. It is required by the manufacturer of standard reverse-osmosis filters that there be at least a certain ratio of water which does not pass through the membrane to water which does pass therethrough, this ratio being achieved by use of a properly-sized constrictor in the waste-water outlet. The waste water contains salts and other impurities flushed from the membrane, and usually flows for at least several hours each day. Therefore, the constricted region tends to plug or clog and prevent the system from operating properly.
Many efforts have been made to solve the clogging problem. Use has been made, for example, of long volute passages having flow cross-sections relatively large in comparison to that of an orifice. As another example, resort has been had to a balanced valve in which a needle element seats axially on a valve seat. Beds of particulate material have been proposed. These and other attempts have been impractical or unsuccessful.
In the present water purifier, there is automatic, fully effective and rapid cleaning of a constricting outflow valve each time the spigot is opened while the storage bladder is full. This occurs sufficiently often to insure that clogging will not be any problem, but sufficiently seldom to prevent substantial wastage of water. Very importantly, the flow area remains at a precise, predetermined value at all times when constriction is desired.
Another major problem in most earlier systems (not the one specified in the cited patent) is that there is a substantial back pressure against the membrane. Therefore, for a given input pressure there will be a reduced pressure differential across the membrane--retarding the rate of filtration. Particularly since (as discussed below) a standard commercial filter requires many minutes to generate one glass of water, even when there is no back pressure, it will be understood that a lessening of this filtering rate is distinctly undesirable.
Many earlier systems (not the one described in the patent) cause waste water to pass through the reverse-osmosis unit twenty-four hours a day. This is, of course, a horrendous waste of water. In addition, the continuous water flow exacerbates the clogging problem discussed above.
It is common in earlier systems to use metal valves having piston or other sliding elements sealed by O-rings. Although O-rings are often satisfactory in many types of machinery, they are unsatisfactory as sliding seals in almost all parts of household water purifier systems. There are two reasons for this, the first being that O-rings (and comparable seals) tend to freeze or stick, thus preventing the system from operating. Secondly, O-rings (in systems where there are low pressure differentials) are best used with metal parts the diameters of which are precise and do not change excessively with temperature. Commercial plastic, which can be cheaply injection-molded, changes diameter--with temperature--to an excessive degree usually making O-rings impractical in water purifiers.
The present system is substantially all plastic, and uses no sliding seals (O-rings or otherwise) except in one part of the second embodiment. The water never "sees" any metal until the stainless-steel spout is reached. The highly-sensitive diaphragm valves cannot stick, and have great reliability and life.
Earlier systems (including the one set forth in the patent) do not block the escape of certain waste water (the pressurizing or "squeeze" water) to the drain during the time when the spigot is open. Such a shut-off, which is achieved by a valve in the second embodiment of the present invention, makes the unit more practical and effective in water-scarcity and/or low water-pressure regions.